1. Field of the Invention
The present invention relates to a robot controller controlling a robot equipped with a travel axis.
2. Description of the Related Art
In industrial robots, a control technique for compensating for deformation or torque of a component part caused by operation of an axis at a different location has been proposed.
Japanese Patent Publication No. 2006-293624A discloses a multi-axis controller controlling a plurality of mutually interfering axes wherein disturbance torque is estimated based on the position commands to other axes and the torques at the individual joints are corrected.
Japanese Patent Publication No. 2009-082997A discloses a robot controller which compares a speed of movement of a hand part of a robot at the different coordinate axes of the Cartesian system with threshold values and when the speed of movement of at least one coordinate axis is larger than a threshold value, makes the robot stop.
Japanese Patent Publication No. 2002-307344A discloses a robot controller performing modeling deeming the joints as springs and correcting the position and posture of the hand of the robot considering the bending at the component parts of the multiarticulated robot.
In a robot equipped with a travel axis, sometimes the travel axis makes the robot move while leaving the tool tip fixed in a certain position in space. FIG. 5 is a view of the robot 100 moving due to the travel axis 110 as seen from above. If referring to FIG. 5, the base of the robot 100 moves by the travel axis 110 from the position shown by the broken line to the position shown by the solid line, while the position of the tip 132 of the tool 130 attached to the arm 120 does not change before and after movement.
At the time such an operation is performed, an interference torque T is generated about the J1 axis of the robot 100 (axis rotating about axis extending vertical to surface at which travel axis is set) (see FIG. 6). If the speed of movement or acceleration of the travel axis 110 is large, due to the effects of the interference torque T, the position of the tip 132 of the tool 130 sometimes shakes as shown by the arrow 140 in FIG. 6. If the position of an operating point shakes in the state with hemming rollers etc. gripping a workpiece, the workpiece is liable to deform into an unintended shape.
If forming the component parts about the J1 axis by a high rigidity material, the shaking of the tool tip due to the interference torque can be suppressed. Further, by performing modeling deeming the joints as springs, it is possible to compensate for shaking of the tool tip if correcting the position of the tool tip considering the bending of the joints.